Avian influenza -- commonly called "
bird flu" or "avian flu" -- is an infection caused by
influenza viruses (avian flu viruses) that occur naturally in birds. Wild birds can carry the avian
flu virus, but usually do not get sick from them. However, some domesticated birds, including chickens, ducks, and turkeys, can become infected with the avian flu virus and die.
Avian Flu: H5N1 in Animals
One strain of avian flu, the
H5N1 virus, is endemic in much of Asia and has recently spread into Europe. Avian
H5N1 infections have recently killed poultry and other birds in a number of countries. Strains of avian H5N1 influenza may infect various types of animals, including wild birds, pigs, and tigers.
Avian flu symptoms in birds and other animals vary, but virulent strains can cause death within a few days.
Avian Flu: H5N1 in Humans
Avian flu H5N1 in humans is currently limited and not a
pandemic. Human H5N1 influenza infection was first recognized in 1997, when this virus infected 18 people in Hong Kong, causing 6 deaths. Since 2003, more than 100 human H5N1 flu cases have been diagnosed in:
- Thailand
- Vietnam
- Cambodia
- Indonesia
- China.
Of those cases, more than half have died as a result of the avian flu virus.
Currently, close contact with infected poultry has been the primary source of human infection for avian flu. Although rare, there have been isolated reports of human-to-human transmission of avian flu. Genetic studies confirm that the influenza A virus H5N1 mutates rapidly, which means that should it adapt to allow easy human-to-human transmission, a pandemic could ensue. At this time, it is uncertain whether the currently circulating H5N1 virus will lead to a global disease outbreak in humans -- a pandemic.
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